Efficacy of transcranial direct current stimulation (tDCS) on upper limb motor control in persons with sub-acute stroke - A randomized controlled trial

Residual upper limb paresis is one of the most common motor impairments that affect stroke survivor’s activities of daily living. Upper limb reaching movement, a necessary component for performing many tasks of daily living is affected in stroke. Reaching movement in survivors with stroke is characterized by abnormal patterns of muscle activation and limitation in joint ranges. These abnormal patterns of muscle activation and limitation in joint ranges may be due to deficits in the range of regulation of tonic stretch reflex thresholds (TSRT) of agonist and antagonist muscles. TSRT is the joint angle at which motorneuronal recruitment begins. Although various physical therapy approaches improves effective use of the arm including reaching, residual reaching movement deficits persist in persons with stroke.

Transcranial direct current stimulation (tDCS), a non-invasive method of brain stimulation helps in enhancing neural plasticity and learning through neuromodulation and by increasing neurotransmitter, receptor and neurotrophin levels. Based on its effects on neural plasticity and learning, we hypothesize that, tDCS combined with upper limb reaching training could improve reaching ability in stroke persons by altering the spatial zones.Hence, the aim of this study is to determine the efficacy of tDCS on upper limb motor control in persons with sub-acute stroke.

This study is a double blinded randomized controlled trial. The participants in the intervention group will receive anodal tDCS along with task specific training with trunk restraint (TRTST) and the control group will receive sham tDCS along with TRTST. Both groups will receive either anode or sham tDCS in the first 30 minutes of a one hour of TRTST session per day for 5 days per week for 4 consecutive weeks. The primary outcome measures are kinematic analysis of elbow extension range during a standardized reach-to-grasp task, Spatial zones such as coactivation zone and silent zone of both agonist and antagonist using Montreal TSRT measure, Chedoke Arm and Hand Activity Inventory (CAHAI- 7 Version) and Action Research Arm Test (ARAT) and secondary measures are Reaching Performance Scale, composite spasticity Index, Upper Extremity Subset of Fugl – Meyer Motor Function Assessment (UE –FMA), Patient Health Questionnaire-9. Both primary and secondary outcome measures will be taken before the first day of the intervention, immediately after the 4 weeks of intervention and after a 1 month follow up period.